A battery, such as a primary battery and a secondary battery, generally includes an electrode group having a positive electrode and a negative electrode, and a package member for storing the electrode group.
A metal can and a laminated film-made container have been commercially used as a package member. A metal can is formed by deep-drawing processing of a metal plate of aluminum, etc. To form a can by deep-drawing processing, a metal plate needs to have a certain thickness; however, this is an obstacle to reducing a thickness of a package, and leads to a loss in volume and capacity. For example, if a package can having a plate the plate thickness in total to the thickness of the battery is 7.7%. Since a package has high rigidity but less flexibility, a gap is often generated between the inner wall of a package can and an electrode group. As a consequence, a gap between a positive electrode and a negative electrode in the electrode group may lead to degradation of a charge-and-discharge cycle. Furthermore, a package with high rigidity is inclined to have defects, such as cracking, when an excess force is applied to the vicinity of a welded portion.
However, because a portion of a laminated film-made container that is sealed by heat sealing may melt at a high temperature, its reliability is insufficient.
Also, the manufacturing costs for both a package can and a laminated film-made container are high.
Under such circumstances, it has been requested to provide a package with an improvement in thickness reduction and flexibility, and with excellent reliability at low manufacturing costs.